Question

The decreasing order of p$K_b$ of the following aromatic amines is

• (a) \textgreater{} (b) \textgreater{} (d) \textgreater{} (c)
• (a) \textgreater{} (c) \textgreater{} (d) \textgreater{} (b)
• (b) \textgreater{} (d) \textgreater{} (c) \textgreater{} (a)
• (b) \textgreater{} (c) \textgreater{} (d) \textgreater{} (a)

Hint:

Electron-donating groups increase basicity, while electron-withdrawing groups reduce it.

Answer 1

The Correct Option is C

Basicity order (reflected by $pK_b$): higher basicity ⇒ higher $pK_b$
- Benzylamine is more basic due to less delocalization of lone pair.
- p-Methoxyaniline has +R effect of –OCH$_3$, increasing basicity.
- p-Nitroaniline has –R/–I effect (electron-withdrawing), decreasing basicity.
- Aniline’s lone pair is delocalized into the ring, reducing its availability.
Thus, order: Benzylamine \textgreater{} p-Methoxyaniline \textgreater{} p-Nitroaniline \textgreater{} Aniline